On May 6, 2010, US stock markets experienced a sudden and inexplicable drop of around 1000 points or 9% of value, the largest one-day drop in stock market history. It recovered within minutes and the whole episode, the so-called Flash Crash, has variously been attributed to human error or technical failure. These explanations are scary enough, but Robert Harris has an even more frightening idea.

Dr Alex Hoffman is a physicist once employed on the Desertron, the Superconducting Super Collider in Texas that was shut down due to budgetary considerations in 1993 and later at CERN on the Large Hadron Collider in Switzerland. His speciality is artificial intelligence or, as he prefers to call it, "autonomous machine reasoning." When he lost the latter job under somewhat obscure circumstances, he abandoned pure science in favour of making money, something he is spectacularly good at. As THE FEAR INDEX opens, he and his hedge fund partner, Hugo Quarry, are about to launch proprietary investment software that will make the fund an annual income of sixty million dollars in return for an hour or so of work and a bit of schmoozing. The algorithm, VIXAL, is Hoffman's doing; the schmoozing is Quarry's department.

The algorithm is designed to account for projected stock market volatility that can be attributed to random events, the "fear index" of the title. So with delightful irony, we find that Hoffman, the man who would make money out of fear, find himself suddenly subjected to an incomprehensible campaign against him, seemingly designed to drive him mad. It all starts innocently enough when he receives a rare Darwin first edition from an anonymous benefactor who later appears to have paid for it out of one of Hoffman's own accounts. But things turn rapidly worse almost immediately when he awakes to discover an intruder in his kitchen, cheerfully sharpening the knives. How could someone have penetrated the state of the art security barrier that surrounds Hoffman's Geneva mansion?

In the course of the encounter, Hoffman suffers a blow to the head and needs a bran scan, something that reveals two very interesting facts. First of all, Hoffman is less than impressed with his own brain: "Its messiness, its lack of form or beauty, depressed him. Surely we can do better than this, he thought. This cannot be the end product. This must be merely a stage in evolution, and our human task is to prepare the way for whatever comes next....". VIXAL is thus an evolutionary step. The scan reveals something else, however - an anomaly that might presage some serious if undefined condition and Hoffman does not want to know. From that point onward, he spirals ever downward, ending in a spectacular conclusion.

When I was reading Robert Harris' POMPEII some years ago, it occurred to me that a writer who could keep me in suspense about whether or not Vesuvius might erupt and take out the city clearly knew what he was about. The same can be said about THE FEAR INDEX. Any writer who can make hedge funds both comprehensible and the stuff of fiction has a formidable talent.

There are a lot of lovely ideas to be pursued here - the fate of the Frankenstein story in the 21st century, the shift of science from enemy of humanism to handmaiden of art, the question of whether Darwinian principles of evolution can extend to machines - but it would take more space than I have to consider them. You will undoubtedly find yourself thinking about all these and more while simultaneously reading on compulsively to the end of this superb thriller. All too often, the "ideas" that animate thrillers are bloated, vague theories of conspiracy, but THE FEAR INDEX, while providing plenty to worry about also provides serious food for thought, not to speak of a potential moment of real terror the next time the stock market craters for no particular reason.

§ Yvonne Klein is a writer, translator, and retired college English professor who lives in Montreal.